Method and an apparatus for processing a signal

ABSTRACT

A method of processing a signal is disclosed, which includes receiving a downmix signal, object information and rendering information; obtaining downmix gain flag information indicating whether a downmix gain is included in the object information; and generating downmix processing information using the object information and the rendering information based on the downmix gain flag information, wherein the object information includes modified object level information or object level information, wherein the modified object level information is determined using a level of a modified object generated by applying the downmix gain to an object, and wherein the object level information is determined using a level of the object. Accordingly, in an apparatus for processing a signal and method thereof according to the present invention, the signal is decoded using modified object level information based on downmix gain flag information. Therefore, the present invention enables to select an efficient signal processing method according to an environment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT/KR2008/007275 filed onDec. 9, 2008, which claims priority under 35 U.S.C. 119(e) to U.S.Provisional Application Nos. 61/012,452 filed on Dec. 9, 2007 and61/020,362 filed on Jan. 10, 2008, all of which are hereby expresslyincorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a method and an apparatus forprocessing an audio signal received via a digital medium, a broadcastsignal or the like.

BACKGROUND ART

Generally, in the process for downmixing at least one object into a monoor stereo signal, parameters are generated by using object. Thesesparameters include object level information indicating a level of theobject and a downmix gain applied to the object.

DISCLOSURE OF THE INVENTION Technical Problem

However, since a downmix signal includes at least one object to whichdownmix gains are applied in encoding, the downmix gain transferred to adecoder may be redundant.

Technical Solution

Accordingly, the present invention is directed to an apparatus forprocessing a signal and method thereof that substantially obviate one ormore of the problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide an apparatus forprocessing a signal and method thereof, by which a transmitted bit forobject information can be reduced in a manner that a downmix gain istransferred by not being included in object information using a modifiedobject generated from applying the downmix gain to an object.

Another object of the present invention is to provide an apparatus forprocessing a signal and method thereof, by which the signal can bedecoded using downmix gain flag information indicating whether a downmixgain is included in object information or modification object levelinformation is included in object information or using modified objectlevel information instead of using a downmix gain.

Advantageous Effects

Accordingly, the present invention provides the following effects oradvantages.

First of all, in an apparatus for processing a signal and method thereofaccording to the present invention, the signal is decoded using objectinformation including modified object level information. Therefore,since a downmix gain is not transferred, the present invention is ableto decode a signal using less information.

Secondly, in an apparatus for processing a signal and method thereofaccording to the present invention, a signal is decoded using objectlevel information and downmix gain or using modified object levelinformation instead of using the downmix gain, according to downmix gainflag information indicating whether the downmix gain is included inobject information. Therefore, the present invention enables to selectan efficient signal processing method according to an environment.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a schematic diagram of a signal encoding apparatus accordingto one embodiment of the present invention;

FIG. 2 is a schematic diagram of an object information generating unitaccording to one embodiment of the present invention;

FIG. 3 is a flowchart for a signal encoding method in the objectinformation generating unit shown in FIG. 2;

FIG. 4 is a schematic diagram of an object information generating unitshown in FIG. 2 according to another embodiment of the presentinvention;

FIG. 5 is a flowchart for a signal encoding method in the objectinformation generating unit shown in FIG. 4;

FIG. 6 is a schematic diagram of a signal decoding apparatus accordingto another embodiment of the present invention;

FIG. 7 is a diagram of a structure of syntax according to anotherembodiment of the present invention; and

FIG. 8 is a flowchart of a signal decoding method according to FIG. 6.

BEST MODE

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims thereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a method ofprocessing an audio signal according to the present invention includesreceiving a downmix signal, object information and renderinginformation; and generating downmix processing information using theobject information and the rendering information, the object informationincluding modified object level information, wherein the modified objectlevel information is determined using a level of a modified objectgenerated by applying a downmix gain to an object.

According to the present invention, the downmix gain determines acontribution degree of the object for generating the downmix signal.

According to the present invention, if a downmix signal is a stereosignal, the object information further includes object gain differenceinformation indicating a ratio of contributing the modified object toleft channel and right channel of the stereo signal.

According to the present invention, the object information does notinclude the downmix gain applied to the object. According to the presentinvention, the method can further include generating multi-channelinformation using the object information and the rendering information,the object information including the modified object level information;processing the downmix signal using the downmix processing information;and decoding a multi-channel audio signal by applying the multi-channelinformation to the downmix signal.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, an apparatus for processing an audiosignal includes an object information processing unit generating downmixprocessing information and multi-channel information using objectinformation and rendering information; and a downmix signalpre-processing unit processing a downmix signal using the downmixprocessing information, wherein the object information includes modifiedobject level information determined using a level of a modified object,the modified object is generated by applying a downmix gain to anobject.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, a method of processing an audio signalincludes receiving a downmix signal, object information and renderinginformation; obtaining downmix gain flag information indicating whethera downmix gain is included in the object information; and generatingdownmix processing information using the object information and therendering information based on the downmix gain flag information,wherein the object information includes modified object levelinformation or object level information, wherein the modified objectlevel information is determined using a level of a modified objectgenerated by applying the downmix gain to an object, and wherein theobject level information is determined using a level of the object.

According to the present invention, the object information includes themodified object level information, if the downmix gain flag informationindicates that the downmix gain is not included in the objectinformation. According to the present invention, the object informationfurther includes object gain difference information indicating a ratioof contributing left channel and right channel of a stereo signal, ifthe downmix signal is a stereo signal.

According to the present invention, the object information includes theobject level information and further includes the downmix gain appliedto the object, if the downmix gain flag information indicates that thedownmix gain is included in the object information

According to the present invention, the downmix gain exists in a headerof a bitstream of the audio signal.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, an apparatus for processing an audiosignal includes an object information processing unit generating downmixprocessing information and multi-channel information using objectinformation and rendering information; and a downmix signalpre-processing unit processing a downmix signal using the downmixprocessing information, wherein the object information includes modifiedobject level information determined using a level of a modified objector object level information determined using a level of an object, basedon downmix gain flag information indicating whether a downmix gain isincluded in the object information.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

MODE FOR INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. First of all, terminologies or words used in thisspecification and claims are not construed as limited to the general ordictionary meanings and should be construed as the meanings and conceptsmatching the technical idea of the present invention based on theprinciple that an inventor is able to appropriately define the conceptsof the terminologies to describe the inventor's invention in best way.The embodiment disclosed in this disclosure and configurations shown inthe accompanying drawings are just one preferred embodiment and do notrepresent all technical idea of the present invention. Therefore, it isunderstood that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents at the timing point of filing thisapplication.

First of all, it is understood that the concept ‘coding’ in the presentinvention includes both encoding and decoding.

Secondly, ‘information’ in this disclosure is the terminology thatgenerally includes values, parameters, coefficients, elements and thelike and its meaning can be construed as different occasionally, bywhich the present invention is non-limited. Stereo signal is taken as anexample for a signal in this disclosure, by which examples of thepresent invention are non-limited. For example, a signal in thisdisclosure may include a multi-channel signal having at least three ormore channels.

FIG. 1 is a schematic diagram of a signal encoding apparatus 100according to one embodiment of the present invention.

Referring to FIG. 1, a signal encoding apparatus 100 includes an objectinformation generating unit 110 and a downmix signal generating unit120.

The object information generating unit 110 receives at least one objectand a downmix gain and then generates object information (OI). Theobject information can include downmix gain and object level informationindicating a level of the object. Besides, the object informationgenerating unit 110 is able to generate a modified object by applyingthe downmix gain to the object. In this case, the object informationincludes modified object level information regarding to the modifiedobject instead of the object level information. Details of this processwill be explained with reference to FIGS. 2 to 5 later.

The downmix signal generating unit 120 receives a downmix gain and atleast one object and then generates a downmix signal (DMX). In thiscase, the downmix signal can include a mono or stereo signal, by whichexamples of the present invention are non-limited.

FIG. 2 is a schematic diagram of an object information generating unit110 according to one embodiment of the present invention. Referring toFIG. 2, an object information generating unit 110 includes a modifiedobject generating unit 210 and a modified object level informationgenerating unit 220.

As shown in FIG. 2, the modified object generating unit 210 receives adownmix gain D_(i) and at least one object S_(i) and then generates amodified object Ŝ_(i) by applying the downmix gain D_(i) to the objectS_(i). The modified object Ŝ_(i) can be represented as Formula 1.Ŝ _(i) =D _(i) S _(i)  [Formula 1]

In this case, ‘i’ is the number that indicates each object. Forinstance, a first object can be represented as S₁, a second object canbe represented as S₂, a downmix gain applied to the first object can berepresented as D₁, and a downmix gain applied to second object can berepresented as D₂.

The modified object level information generating unit 220 generatesmodified object level information using a level of the modified object.

Conventional object level information (OLI) is generated from an objectbefore a downmix gain is applied. On the contrary, modified object levelinformation (MLOI) according to one embodiment of the present inventionis estimated from a modified object generated by applying a downmix gainto an object Ŝ_(i).

The conventional object level information (OLD) estimated from theobject and the modified object level information (MOLD) estimated fromthe modified object according to one embodiment of the present inventionare represented as Formula 2 and Formula 3, respectively, as follows.

$\begin{matrix}{{{OLD}_{i}({pb})} = \frac{\sum\limits_{n}{\sum\limits_{m \in {pb}}{s_{i}^{n,m}s_{i}^{n,m^{*}}}}}{\max\limits_{k}\left( {\sum\limits_{n}{\sum\limits_{m \in {pb}}{s_{k}^{n,m}s_{k}^{n,m^{*}}}}} \right)}} & \left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack \\{{{MOLD}_{i}({pb})} = \frac{\sum\limits_{n}{\sum\limits_{m \in {pb}}{{\hat{s}}_{i}^{n,m}{\hat{s}}_{i}^{n,m^{*}}}}}{\max\limits_{k}\left( {\sum\limits_{n}{\sum\limits_{m \in {pb}}{{\hat{s}}_{k}^{n,m}{\hat{s}}_{k}^{n,m^{*}}}}} \right)}} & \left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In this case, ‘S_(i) ^(n,m)’ indicates an object on a sub-band definedby a time slot ‘n’ and a sub-band ‘m’. In this following description,the ‘n’ and ‘m’ are omitted from the corresponding expression.

As mentioned in the foregoing description, modified object levelinformation (MOLD) indicates a level of a modified object to which adownmix gain is applied. And, it will be more efficient in aspect ofcoding efficiency when a modified object is controlled with objectinformation and rendering information in decoding. Therefore, objectinformation according to one embodiment of the present inventionincludes modified object level information (MOLD) regarding to amodified object generated by applying a downmix gain to an object so asnot to be separately transferred

FIG. 3 is a flowchart for a signal encoding method in the objectinformation generating unit shown in FIG. 2.

Referring to FIG. 3, an object and a downmix gain are received [S310]. Amodified object is then generated by applying the downmix gain to theobject according to Formula 1 [S320]. And, it is able to generatemodified object level information from the generated modified objectaccording to Formula 3 [S330].

Moreover, it is able to generate a downmix signal (DMX) using themodified object [S340]. The downmix signal can include a simple sum ofthe objects and can be represented as Formula 4, by which the presentinvention is non-limited.DMX=ΣŜ _(i)  [Formula 4]

Object information (OI), which is the information on at least oneobject, includes inter-object cross correlation information (IOC)indicating similarity degree between channels of object, absolute objectenergy information (NRG) indicating a reference level value fornormalizing a level of an object, object level information (OLD)indicating a level of an object, a downmix gain (DMG) indicating acontribution degree of an object to channel of a downmix signal, anddownmix gain difference information (DCLD) indicating gain difference ofobject contributing to at least two downmix channels in case that adownmix signal is stereo signal.

And, object information (OI) according to one embodiment of the presentinvention can further include modified object level information (MOLD)indicating a level of a modified object generated by applying a downmixgain to an object. Besides, in case that the object information (OI)includes the modified object level information (MOLD), the objectinformation (OI) may not include a downmix gain (DMG). Therefore, asignal processing method and apparatus according to one embodiment ofthe present invention can reduce a transmitted bit for objectinformation in a manner that a downmix gain (DMG) is not transferred toa decoder side.

FIG. 4 is a schematic diagram of an object information generating unit110 according to another embodiment of the present invention.

Referring to FIG. 4, an object information generating unit 110 includesa modified object generating unit 410, a modified object levelinformation generating unit 420 and an object gain differenceinformation generating unit 430.

The modified object generating unit 410, as shown in FIG. 4, receives anobject S_(i) and a downmix gain D_(i) and then generates a modifiedobject Ŝ_(i) by applying the downmix gain D_(i) to the object S_(i). Incase that at least one object generates a stereo downmix signal bydownmixing, the downmix gain D_(i) is the value indicating acontribution degree of an object to a stereo channel and may include apair of values. In this case, in order to generate a modified object, itis able to derive modified downmix gains ({circumflex over (D)}_(1,i),{circumflex over (D)}_(2,i)) to apply a normalized gain value using thedownmix gains. This can be represented as Formula 5.{circumflex over (D)}_(1,i) =D _(1,i)/√{square root over (D _(1,i) ² =D_(2,i) ²)} {circumflex over (D)}_(2,i) =D _(2,i)/√{square root over (D_(1,i) ² =D _(2,i) ²)}  [Formula 5]

Moreover, in order to generate a modified object Ŝ_(i), the modifieddownmix gains {circumflex over (D)}_(1,i) and {circumflex over(D)}_(2,i) can be the normalized value represented as Formula 6.{circumflex over (D)} _(1,i) ² ={circumflex over (D)} _(2,i)²=1  [Formula 6]

The modified object generating unit 410 is able to generate a modifiedobject Ŝ_(i) using the modified downmix gains normalized as Formula 6.This can be represented as Formula 7.ŝ_(i)=√{square root over (D _(1,i) ² =D _(2,i) ²)}s _(i)  [Formula 7]

Moreover, modified objects Ŝ_(1,i) and Ŝ_(2,i) being included in astereo downmix signal can be derived by Formula 8.ŝ _(1,i) ={circumflex over (D)} _(1,i) ŝ _(i) ŝ _(2,i) ={circumflex over(D)} _(2,i) ŝ _(i)  [Formula 8]

In Formula 8, Ŝ_(1,i) and Ŝ_(2,i) may be the modified objects beingincluded in left channel and right channel (Ŝ_(1,i), Ŝ_(2,i)) of thestereo downmix signal, respectively. They can be determined by themodified downmix gains {circumflex over (D)}_(1,i) and {circumflex over(D)}_(2,i).

The modified object level information generating unit 420 generatesmodified object level information (OLD) by estimating modified objectlevel information using the modified object Ŝ_(i). In case that agenerated downmix signal is a stereo signal, the object gain differenceinformation generating unit 430 is further included. The object gaindifference information generating unit 430 derives object gaindifference information (DCLD) not using the modified downmix gains{circumflex over (D)}_(1,i) and {circumflex over (D)}_(2,i) used togenerate a modified object but using downmix gains D_(1,i) and D_(2,i)inputted to the modified object generating unit 410. The derived objectgain difference information (DCLD) is represented as Formula 9, by whichexamples of the present invention are non-limited. Moreover, it is ableto derive object gain difference information (DCLD) using the amendeddownmix gains {circumflex over (D)}_(1,i) and {circumflex over(D)}_(2,i) as well.

$\begin{matrix}{{DCLD}_{i} = {10{\log_{10}\left( \frac{D_{1,i}^{2}}{D_{2,i}^{2}} \right)}}} & \left\lbrack {{Formula}\mspace{14mu} 9} \right\rbrack\end{matrix}$

The modified object level information (MOLD) generated by the modifiedobject level information generating unit 420 and the object gaindifference information (DCLD) generated by the object gain differenceinformation generating unit 430 can be contained in the objectinformation (OI) and be transmitted. On the contrary, the objectinformation (OI) includes the modified object level information (MOLD)only without including the object level information (OLD) and thedownmix gain (DMG) to a decoder side. Therefore, it is able to reduce aused bit for object information.

FIG. 5 is a flowchart for a signal encoding method in the objectinformation generating unit shown in FIG. 4.

Referring to FIG. 5, an object and a downmix gain are received [S510]. Amodified object is then generated by applying the downmix gains to theobject according to Formula 7 [S520].

Subsequently, it is able to generate modified object level information(MOLD) and a downmix signal (DMX) using the modified object [S530]. Themodified object level information (MOLD) indicates a level of a modifiedobject by applying a downmix gain to an object.

If the modified object level information is included in objectinformation (OI), a downmix gain (DMG) may not be included in the objectinformation. In this case, the downmix signal (DMG) can be simplygenerated from a sum of modified objects.

And, it is able to generate downmix gain difference information (DCLD),as represented as Formula 9, using downmix gains. In this case, thedownmix gain difference information (DCLD) indicates a gain differenceof an object contributing to each channel of a downmix signal.

As mentioned in the above description, in a signal processing method andapparatus according to another embodiment of the present invention, amodified object is generated and used, whereby a downmix gain (DMG) isnot transmitted to a decoder side. If a downmix signal is a mono,modified object level information (MOLD) is transmitted. If a downmixsignal is a stereo signal, modified object level information (MOLD) anddownmix gain difference information (DCLD) are transmitted. Therefore,the present invention is able to reduce a used bit for objectinformation.

FIG. 6 is a schematic diagram of a signal decoding apparatus 600according to an embodiment of the present invention.

Referring to FIG. 6, a signal decoding apparatus 600 includes an objectinformation processing unit 610, a downmix signal pre-processing unit620 and a multi-channel decoding unit 630.

The object information processing unit 610 receives object information(OI) and rendering information (RI) and then generates downmixprocessing information (DPI) and multi-channel information (MI) by usingobject information and rendering information.

In this case, the object information (OI) can include object levelinformation (OLD), downmix gain (DMG) and downmix gain differenceinformation (DCLD). On the other hand, in case that modified objectlevel information (MOLD) is included in the object information (OI)instead of object level information (OLD), the downmix gain (DMG) is notincluded. Only if a downmix signal is a stereo signal, the objectinformation (OI) can further include the downmix gain differenceinformation (DCLD).

Whether the object information (OI) includes the modified object levelinformation (MOLD) or whether the object information (OI) includes thedownmix gain (DMG) can be determined based on downmix gain flaginformation (DMG_flag). Details of this process will be explained withreference to FIG. 8 later.

In case that a downmix signal is a stereo signal, the downmix processinginformation (DPI) generated by the object information processing unit610 is used to control a signal on one channel of the stereo signal tothe other channel [hereinafter, this is called ‘panning’].

Based on the downmix gain flag information (DMG_flag), the objectinformation processing unit 610 generates multi-channel information (MI)for upmixing a downmix signal into a multi-channel signal using objectinformation (OI) further including absolute level information (absoluteobject energy: NRG) indicating an energy level of an object having ahighest energy level and inter-object correlation information(inter-object cross correlation: IOC) as well as the modified objectlevel information (MOLD) and the downmix gain difference information(DCLD). In this case, the multi-channel information (MI) is able toinclude inter-channel level difference information (CLD), inter-channelcorrelation information (ICC) and channel prediction information (CPC).

On the other hand, based on the downmix gain flag information, it isable to generate multi-channel information (MI) using object information(OI) that includes object level information (OLD), downmix gain (DMG)and downmix gain difference information (DCLD).

The downmix signal pre-processing unit 620 receives the downmix signal(DMX) and the downmix processing information (DPI) and is then able togenerate a processed downmix signal (processed DMX: PDMX). The downmixprocessing information (DPI) is applied to the downmix signal to controlfor panning an object and a level of an object. Therefore, the downmixprocessing information (DPI) is applicable only if the downmix signal isa stereo signal.

The multi-channel decoding unit 630 is able to decode an audio signalhaving a multi-channel by applying the multi-channel information (MI) tothe processed downmix signal (PDMX) outputted from the downmix signalpre-processing unit 620. The multi-channel decoding unit 630 is usableonly if an output signal is an audio signal that has at least threemulti-channels.

On the other hand, if an output signal is a mono or stereo signal, themulti-channel decoding unit 630 is bypassed but the downmix signalgenerated from the downmix signal pre-processing unit 620 is outputtedintact.

FIG. 7 is a diagram of a structure of syntax according to anotherembodiment of the present invention.

Referring to FIG. 7, in case that modified object level information isincluded in object information, an audio signal is decoded not a downmixsignal but using a modified object. Therefore, it is able to reduce aused bit for object information being transmitted to a decoder.

FIG. 8 is a flowchart of a signal decoding method according to FIG. 6.

Referring to FIG. 8, a downmix signal, object information and renderinginformation are received [S810]. Downmix gain flag information(DMG_flag) is obtained from the object information and a setup value isthen checked [S820]. The downmix gain flag information (DMG_flag) mayindicate whether the downmix gain (DMG) is included in the objectinformation (OI) or whether the modified object information [MOLD] isincluded in the object information (OI).

Meanings of the downmix gain flag information (DMG_flag) are representedin Table 1 and Table 2.

TABLE 1 DMG_flag Meaning 1 DMG is included in OI. 0 DMG is not includedin OI.

TABLE 2 DMG_flag Meaning 1 OLD is included in OI (MOLD not included). 0MOLD is included in OI.

Based on the downmix gain flag information, if the downmix gain is notincluded in the object information [‘yes’, if DMG_flag=1], modifiedobject level information (MOLD) on the modified object (Ŝ_(i)) isextracted from the object information [S830]. If the downmix gain isincluded in the object information [‘no’, if DMG_flag=1], object levelinformation (OLD) on the object and the downmix gain (DMG) are extractedfrom the object information (OI) [S840].

Moreover, the downmix gain flag information, as shown in Table 2, isable to indicate whether modified object level information (MOLD) isincluded in object information (OI).

In this case, based on the downmix gain flag information (DMG_flag), ifthe modified object level information (MOLD) is included in the objectinformation (OI) and if the object level information (OLD) is notincluded in the object information (OI) [‘yes’, if DMG_flag=1], modifiedobject level information (MOLD) on a modified object (Ŝ_(i)) isextracted from the object information [S830].

If the modified object level information (MOLD) is not included in theobject information (OI) and if the object level information (OLD) isincluded in the object information (OI) [‘no’, if DMG_flag=1], objectlevel information (OLD) on the object and the downmix gain (DMG) areextracted from the object information [S840].

Subsequently, using the extracted modified object level information(MOLD) or the extracted object level information (OLD) and downmix gain(DMG), a multi-channel audio signal is decoded [S850]. In case that thedownmix signal is a stereo signal, it is able to decode a multi-channelaudio signal by further extracting to use downmix gain differenceinformation from the object information (OI).

Thus, in a signal processing method and apparatus according to anotherembodiment of the present invention, a signal is decodable using objectlevel information (OLD) and downmix gain (DMG) or modified object levelinformation (MOLD) in accordance with downmix gain flag information(DMG_flag) obtained from object information (On. Therefore, the presentinvention enables a signal to be efficiently processed according to anenvironment.

Moreover, a downmix gain can be included in each frame. If a method ofgenerating a downmix signal is uniform within a predetermined time, asingle file, a single song or the like, the downmix gain can be constantwithin a same interval. In this case, including a downmix gain in aframe at a timing point of applying a modified downmix gain will be moreeffective than including a downmix gain in each frame.

Therefore, a signal processing method/apparatus according to a furtherembodiment of the present invention can further include downmix gainupdate flag information (DMG_update_header_flag) indicating whether adownmix gain is updated per frame.

The downmix gain update flag information (DMG_update_header_flag)indicates how the downmix gain is included in the corresponding frameand can be included in a header area of a bitstream. Moreover, themeaning of the downmix gain update flag information can be representedas Table 3, by which examples of the present invention are non-limited.

TABLE 3 DMG_update_header_flag Meaning 0 DMG is same in every frame. 1Determine whether DMG is updated, based on downmix gain flag informationincluded in frame 2 DMG is updated per predetermined period (frames). 3DMG is updated per frame.

Referring to Table 3, if a downmix gain update header flag is set to 0,a downmix gain is same in every frame with a uniform value that is notupdated. Hence, a downmix gain (DMG) can be included not in a frame areabut in a header area. If a downmix gain update header flag is set to 1,downmix gain frame flag information (DMG_update_frame_flag) indicatingwhether a downmix gain is updated per frame can be further included. Ifthe downmix gain frame flag information indicates that a correspondingframe includes an updated downmix gain, object information is able toinclude the updated downmix gain.

If a downmix gain update header flag is set to 2, a downmix gain updatedper predetermined frame period set in a header can be included. If adownmix gain update header flag is set to 3, an updated downmix gainupdated per frame is included to be usable.

The downmix gain should be understood to generally indicate informationrelevant to a downmix gain for efficient coding as well as a value ofthe downmix gain. For instance, in case of using differential codingscheme, a differential value, an interpolation value, an indicator forgenerating a previous value or the like can be included.

In case that a downmix gain is same in every frame, a downmix gain canbe included in a header area without having downmix gain header flaginformation included in a header area of a bitstream.

The present invention applied decoding/encoding method can beimplemented in a program recorded medium as computer-readable codes.And, multimedia data having the data structure of the present inventioncan be stored in the computer-readable recoding medium. Thecomputer-readable recording media include all kinds of storage devicesin which data readable by a computer system are stored. Thecomputer-readable media include ROM, RAM, CD-ROM, magnetic tapes, floppydiscs, optical data storage devices, and the like for example and alsoinclude carrier-wave type implementations (e.g., transmission viaInternet). And, a bitstream generated by the encoding method is storedin a computer-readable recording medium or can be transmitted viawire/wireless communication network.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

INDUSTRIAL APPLICABILITY

Accordingly, the present invention is applicable to encoding anddecoding of signals.

What is claimed is:
 1. A method of processing an audio signal,comprising: receiving a downmix signal, object information and renderinginformation; obtaining downmix gain flag information indicating whethera downmix gain is included in the object information; generating downmixprocessing information using the object information and the renderinginformation based on the downmix gain flag information; generatingmulti-channel information using the object information and the renderinginformation; generating a processed downmix signal using the downmixprocessing information and the downmix signal; and decoding amulti-channel audio signal by applying the multi-channel information tothe processed downmix signal, wherein the object information includesmodified object level information or object level information, whereinthe modified object level information is determined using a level of amodified object generated by applying the downmix gain to an object,wherein the object level information is determined using a level of theobject, wherein the object information further includes object gaindifference information indicating a ratio of contributing a left channeland a right channel of a stereo signal, if the downmix signal is astereo signal, and wherein the object information includes the modifiedobject level information, if the downmix gain flag information indicatesthat the downmix gain is not included in the object information.
 2. Themethod of claim 1, wherein the object information includes the objectlevel information and further includes the downmix gain applied to theobject, if the downmix gain flag information indicates that the downmixgain is included in the object information.
 3. The method of claim 2,wherein the downmix gain exists in a header of a bitstream of the audiosignal.
 4. An apparatus for processing an audio signal, comprising: anobject information processing unit generating downmix processinginformation and multi-channel information using object information andrendering information; a downmix signal pre-processing unit generating aprocessed downmix signal using a downmix signal and the downmixprocessing information; and a multi-channel decoding unit decoding amulti-channel audio signal by applying the multi-channel information tothe processed downmix signal generated from the downmix signalpre-processing unit, wherein the object information includes modifiedobject level information determined using a level of a modified objector object level information determined using a level of an object, basedon downmix gain flag information indicating whether a downmix gain isincluded in the object information, and wherein the object informationfurther includes object gain difference information indicating a ratioof contributing a left channel and a right channel of a stereo signal,if the downmix signal is a stereo signal, and wherein the objectinformation includes the modified object level information determined bythe modified object, the modified object generated by applying thedownmix gain to the object, if the downmix gain flag informationindicates that the downmix gain is not included in the objectinformation.
 5. The apparatus of claim 4, wherein the object informationincludes the object level information determined by using a level of theobject, if the downmix gain flag information indicates that the downmixgain is included in the object information.
 6. A method of processing anaudio signal, comprising: generating a modified object by applying adownmix gain to an object; generating a downmix signal using themodified object; and generating object information using the modifiedobject, wherein the object information includes modified object levelinformation determined by a level of the modified object and downmixgain flag information indicating whether the object information includesthe downmix gain, and wherein the object information further includesobject gain difference information indicating a ratio of contributing aleft channel and a right channel of a stereo signal, if the downmixsignal is a stereo signal, and wherein the object information does notinclude the downmix gain, if the downmix gain flag information indicatesthat the downmix gain is not included in the object information.
 7. Anapparatus for processing an audio signal, comprising: a modified objectgenerating unit generating a modified object by applying a downmix gainto an object; and a modified object level information generating unitdetermining modified object level information by using a level of themodified object and generating downmix gain flag information indicatingwhether the downmix gain is transferred, wherein the modified objectlevel information further includes object gain difference informationindicating a ratio of contributing a left channel and a right channel ofa stereo signal, if a downmix signal is a stereo signal, and whereinobject information includes the modified object level informationdetermined by the modified object, if the downmix gain flag informationindicates that the downmix gain is not included in the objectinformation.
 8. A non-transitory computer-readable recording mediumincluding a program recorded therein, wherein the program is configuredto execute the steps according to claim 1.